Protecting electric apparatus



1927' M. BUCHHOLZ PROTECTING ELECTRIC APPARATUS Filed April 16, 1925 lrr yen/0r Max Bur/w 9/2 iffy, Y

Patented Aug. 23, 1927.

UNITED STATES PATENT OFFICE.

MAX BUGHHOLZ, F CASSEL, GERMANY.

PROTECTING ELECTRIC APPARATUS.

Application filed April 16, 1925, Serial No. 23,682, and in Germany February 5, 1923.

Myinvention has reference to a method and means for protecting electric apparatus Dperating in an insulating liquid, such as ,oil transformers, oil switches, grounding 6 throttling coils, resistances and the like, and

it is one of the important objects of my invention to provide a device of very simple construction and great reliability, and adapted to operate before extensive injuries 1 to the apparatus to be protected can occur by sparking, overloading or other disturbances.

My invention is particularly based on the fact that in the case of disturbances in the operation of the ap aratus to b protected or in the case of spar 'ng or other irregularities of operation, or whenever such irregularities are imminent, as well as in the case of any ebullition or fermentation processes in the oil, serving as'an insulating liquid, bubbles of gases of decomposition are formed which can operate a protective 4 means, for instance an electric contact, either a working or a closed contact, which is adapted to switch out of circuit the apparatus tobe protected, or which will operate an alarm or annunciator' device indicating the disturbance, or which is adapted to effect both kindsof operations. The oil vapors generated or the gases formed by decomposition may influence the contacting means in different ways.

' I may simultaneously cause the bubbles of gases aforesaid to act towards protecting the'liquid insulated apparatus also against injury arising from a lowering of the liquid level in consequence-of the vessel containing the liquid leaking. In such a case the windings and other. current carrying parts might project from the insulating medium and might be heated unduly. In order to provide for such an emergency, I prefer employing a float arranged to be displaced and to close the contact of a; protective circuit in case that insulating liquid .should escape from th vessel or that the liquid level should be lowered from other causes.

In the drawings afiixed to this specification and forming part thereof, two devices embodying my invention are illustrated diagrammatica 1y by way of example.

In the drawings- Fig. 1 is an elevation of a transformer casing and contacting device, while Fig. 2 is a vertical section of this device drawn to a larger scale.

Fig. 3 is a diagram of an upper corner of the transformer vessel with a different float arrangement mounted therein.

Referring to the drawings, a isthe transformer casing or vessel containing the transformer and a supply of insulating liquid such as oil, 72- is the cover closing the vessel and a, c are the insulators for the leadingin conductors. d is a pipe mounted on the cover 6 and communicating with the interior of the vessel a, this pipe leading to an expansion vessel 6 secured to the wall 7.

In order to provide that the gas bubbles liberated in the oil accumulate below and rise in the pipe d, I prefer mounting the vessel a with its cover 6 in an oblique position.

r is a three-way pipe inserted in the pipe d and carrying a tap cock 9 and a calibrated glass cylinder g completely filled with insulating liquid, the liquid level in the expansion vessel 'e being higher than the top end of c linder g. u is a ring-shaped collar mounte in the lower half of the cylinder 9'. -t is a float guided in bearings s and carrying a collar 72. adapted to apply itself from below against the collar to. i is a contact bar secured to the spindle in guiding the float t and o, '0 are the terminals of a protective circuit comprising an alarm or other annunciator device or a switch, fust or the like (not shown). I

7 is another float suspended from a point a: near the lower end of cylinder (1 by an arm m attached to the float g, on one side so that this float, provided that the threeway pipe were not filled with liquid, would assume an oblique position shown in dotted lines, where it would make contact with a contact piece a forming one of the terminals. of the protective circuit before described, the other terminal being connected with the float itself at 'm. o is an abutment preventing the float from moving angularly beyond the position shown in the drawings. w is a cock mounted on the cap p closing the glass cylinder.

Assuming the insulating liquid which surrounds theapparatus to be protected to suf fer decomposition, owing to unnormal working conditions of thls apparatus, gases, vapors or fumes will be developed in the liquid and will rise above the liquid level, collecting below the cover I) and rising first m the pipe at and thereafter in the glass cylinder g. The formation of such bubbles can therefore be ascertained easily and the color and general character of the gases, vapors or fumes will indicate the nature of the material subjected to decomposition. The bubbles of gases or vapors rising in the cylinder 9 will first collect between the cylinder wall, the float t and the collar to, at the same time displacing the oil surrounding the float. This will cause the float to descend and indoing so to close the contacts o and the protective circuit, thereby operating the switch, fuse or annunciator device inserted in this circuit. This position of the float is shown in dotted lines. At the same time the gas bubbles are free to pass between the collars it and u and to collect below the cap 10. However if a larger quantity of gases or vapors is rapidly developed in the oil or other insulating liquid,

it will in entering the three-way tube 1- force or throw the float close the contact at a.

In case that the liquid level in the threeway pipe '1' should sink so as to uncover the float 3;, this float, owing to its particular mode of suspension will be free to move into the position shown in dotted lines where it meets the contact 2, thereby closing the protective circuit and either switching out the transformer or annunciating the defect.

Referring now to Fig. 3,a large float 1 is linked to the wall of the oil filled vessel a by means of a link 2. A small float 3 is articulated to the large float 1 by means of a link 4. One terminal of a protective circuit comprising a switch, fuse, alarm or other annunciator device is connected with link 2 and a contact piece 5 is mounted on the float 1. The other terminal of the protective circuit is connected to the small float 3 which carries a contact piece 6 arran 'ed in close vicinity to contact piece 5. Another contact 7 is arranged in the liquid below a contact piece 53 secured to the bottom of the large float 1.

If bubbles of gases or vapors of decompo sition are liberated in the insulating liquid and rise to the surface, they will cause an irregular movement of the liquid near the surface, whereby the small float 3, owing to its light mass, will be set rocking, thereby establishing 5t t between the terminals 6 and 5 and closing the protective circuit.

If on the other the liquid. level, owing to leakage or from other causes, should be lowered, the la a float i lowered also and the bottom contact piece 3 aside and thereby 8 will meet the contact thereby closiuc protective circuit. Thus both ii in Fig. 2 and the floats l, 3 in 3 a a dual purpose,

viz. answering the sudden formation of larger quantities of gases or vapors and the lowering of the liquid level owing to leakage.

The contacting device according to this invention may be arranged at different places, either in the interior of the main oil receptacle or, in the case of transformers, in combination with expansion vessels contained therein, or special spaces, tubes or similar instrumentalities may be provided adapted for the reception of the contacting devices. The closing of the circuit may be effected both within as well as outside of the liquid.

The circuit to be controlled by the contacts referred to may excite either directly or by the medium of an intermediate relay the releasing coil of an oil switch which interrupts the endangered circuit. In the case of apparatus the circuit of which does not included an oil'switch, as frequently occurs, for instance in the cases of transformers mounted in the field at wide distances apart, other provisions should be made for the purposes of this invention.

Besides the form of construction herein shown and described, the invention is susceptible of a variety of other modifications and forms of application of theprinciple of my invention all of which operate substantially in a similar manner. The means of'connecting the contacting device with the releasing circuit and the switching means are open to changes and alterations without any material importance for the operation of the apparatus according to my invention which in its broad aspects comprises the operation of safety devices for electric apparatus or the like, adapted for operation by vapors, fumes, gases or similar emanations liberated and expelled from the insulating medium, and means adapted to be operatively influenced by such emanations, and connected to fuses or equivalent safety means, the instrumentaliti'es shown and described in this specification as embodiments of these principles being susceptible of modifications without deviating from the spirit of my invention as set forth in the claims.

In the claims the term gases is meant to comprise also vapors and fumes.

I claim 1. Protective system for liquid insulated electric apparatus comprising a vessel containing liquid surrounding the apparatus, a protective circuit including a float system comprising a float and a contact adapted to cooperate with said float in varying the operative conditions of said circuit, said float held in inoperative condition by liquidand being arranged to become operative both a lowering of the liquid level at sudden of the 2. Protective system for liquid insulated float linked "to said first float and cooperelectrio apparatus comprising a vessel oonative contacts. on said floats, said floats betaining liquid surrounding the apparatus, a ing normally held in inoperative position by 10 protecth'e circuit, a float linked to the wall the liquid.

5 of said vessel, a terminal contact of said cir- In testimony whereof I aflix my signature.

suit in said vessel adjacent to said float, a t contact piece on said float; a second smaller MAX BUCHHULZ. 

